Diabetes mellitus is a chronic metabolic disorder caused by an inability of a person's pancreas to produce sufficient amounts of the hormone, insulin, such that the person's metabolism is unable to provide for the proper absorption of sugar and starch. This failure leads to hyperglycemia, i.e. the presence of an excessive amount of analyte within the blood plasma. Persistent hyperglycemia has been associated with a variety of serious symptoms and life threatening long-term complications such as dehydration, ketoacidosis, diabetic coma, cardiovascular diseases, chronic renal failure, retinal damage and nerve damages with the risk of amputation of extremities. Because healing is not yet possible, a permanent therapy is necessary that provides constant glycemic control in order to constantly maintain the level of blood analyte within normal limits. Such glycemic control is achieved by regularly supplying external drugs to the body of the patient to thereby reduce the elevated levels of blood analyte.
Conventionally, an external biologically effective drug (e.g., insulin or its analog) is commonly administered by means of multiple, daily injections of a mixture of rapid and intermediate acting drug via a hypodermic syringe. While this treatment does not require the frequent estimation of blood analyte, it has been found that the degree of glycemic control achievable in this way is suboptimal because the delivery is unlike physiological hormone production, according to which, hormones enter the bloodstream at a lower rate and over a more extended period of time.
Improved glycemic control may be achieved by the so-called intensive drug therapy which is based on multiple daily injections, including one or two injections per day of a long acting drug for providing a basal level of drug and additional injections of a rapidly acting drug before each meal in an amount proportional to the size of the meal. Although traditional syringes have at least partly been replaced by drug pens, the frequent injections are nevertheless very inconvenient for the patient, particularly those who are incapable of reliably self-administering injections.
Substantial improvements in diabetes therapy have been achieved by the development of other drug delivery devices, such as insulin pumps, relieving the patient of the need for syringes or drug pens and the administration of multiple, daily injections. Insulin pumps allow for the delivery of insulin in a manner that bears greater similarity to the naturally occurring physiological processes and can be controlled to follow standard or individually modified protocols to give the patient better glycemic control. In some circumstances, an insulin pump device can store (via input from a clinician or a user) a number of settings (e.g., dosage parameters or other settings) that are customized by the physician for the particular user. In one example, an infusion pump device can be programmed to store a user's insulin sensitivity (e.g., in units of mg/dL/insulin unit), which can be employed by the infusion pump system when calculating a correction bolus dosage for that particular user. In another example, an infusion pump device can be programmed to store a user's carbohydrate ratio (e.g., in units of g/insulin unit), which can be employed by the infusion pump system when calculating meal bolus dosage for that particular user. In many cases, these user-specific settings are manually input into the infusion pump device via user interface buttons on the infusion pump device. If any of these settings are erroneously input into the infusion pump system (e.g., due to a transcribing error or other error when manually inputting the data), the resulting consequences could lead to improper bolus dosage calculations resulting in blood glucose levels that are unnecessarily too high or too low.
In addition, delivery directly into the intraperitoneal space or intravenously can be achieved by drug delivery devices. Drug delivery devices can be constructed as an implantable device for subcutaneous arrangement or can be constructed as an external device with an infusion set for subcutaneous infusion to the patient via the transcutaneous insertion of a catheter, cannula or a transdermal drug transport such as through a patch. External drug delivery devices are mounted on clothing, hidden beneath or inside clothing, or mounted on the body and are generally controlled via a user interface built-in to the device or on a separate remote device.
Drug delivery devices have been utilized to assist in the management of diabetes by infusing drug or a suitable biologically effective material into the diabetic patient at a basal rate with additional drug or “bolus” to account for meals or high analyte values, levels, or concentrations. The drug delivery device typically is connected to an infuser, better known as an infusion set, by a flexible hose. The infuser typically has a subcutaneous cannula, and an adhesive backed mount on which the cannula is attached. The cannula may include a quick disconnect to allow the cannula and mount to remain in place on the skin surface of the user while the flexible tubing is disconnected from the infuser. Regardless of the type of drug delivery device, blood analyte monitoring is typically required to achieve acceptable glycemic control. For example, delivery of suitable amounts of drug by the drug delivery device requires that the patient frequently determine his or her blood analyte level and manually input this value into a user interface for the external drug delivery device, which then may calculate a suitable modification to the default or currently in-use drug delivery protocol, i.e., dosage and timing, and subsequently communicates with the drug delivery device to adjust its operation accordingly. The determination of blood analyte concentration is typically performed by means of an episodic measuring device such as a hand-held electronic meter, which receives blood samples via enzyme-based test strips and calculates the blood analyte value based on the enzymatic reaction. In recent years, continuous analyte monitoring has also been utilized with drug delivery devices to allow for greater control of the drug(s) being infused into the diabetic patients.
People with diabetes and their health care provider (HCP) bear a great deal of cognitive burden in managing intensive drug therapy. Delivering the correct amount of the drug at the correct time is an extremely challenging endeavor. It requires the patient to make dosing determinations multiple times per day and it requires a combination of the patient and the HCP to re-calibrate the therapeutic parameters of the therapy on an episodic time frame that varies from individual to individual.
In light of the many deficiencies and problems associated with current systems and methods for maintaining proper glycemic control, enormous resources have been put into finding better solutions. Developing workable solutions to the problem that are simple, safe, reliable and able to gain regulatory approval has, however, proved to be elusive. For years, researchers have contemplated coupling a continuous glucose monitoring system with an insulin delivery device to provide an “artificial pancreas” to assist people living with diabetes. Their efforts have yet to result in a commercial product. What has been needed is a system and method that provides a level of automatic control of drug delivery devices for improved drug delivery and glycemic control that is simple, safe, and reliable in a real world setting.